1. Field
This invention relates to the recovery of high grade salt from subterranean halite deposits contaminated with calcium and sulfate values. Specifically, it provides a method for recovering salt from such a deposit containing glauberite located in a region suitable for solar evaporation techniques.
2. State of the Art
Halite deposits generally contain calcium- and sulfate-containing minerals such as anhydrite, gypsum, and glauberite. Brines produced by solution mining such deposits typically contain undesirable quantities of dissolved calcium and sulfate values. The usual treatments for removing calcium and sulfate values from such brines involve the addition of reagents. For example, Na.sub.2 CO.sub.3 or Na.sub.2 PO.sub.4 are commonly used to precipitate insoluble calcium compounds. Other reagents, notably BaCl.sub.2, are then added to the brine to precipitate sulfate values. Such chemical treatment methods are expensive and require disposal of the precipitated impurities. Sulfate values may also be removed by mechanical cooling techniques, but such techniques are expensive and create a disposal problem for the sulfate crystal crop thus produced.
Examples of patents disclosing various methods for treating brines are U.S. Pats. Nos. 2,433,601; 2,906,600; 3,024,612; 3,205,013; 3,385,675; and 3,627,479.
It is also known to expose naturally occurring brines to solar evaporation to recover sodium chloride. U.S. Pat. No. 681,407 discloses such a process which involves first removing sulfate of lime in so called "liming ponds" and then crystallizing sodium chloride in other similar ponds. U.S. Pats. 3,484,195 and 3,432,031 disclose the solar evaporation of natural brines whereby sodium chloride is first recovered and then other products, including calcium and sulfate values, are recovered.